以渐进格式保存JPG

Question

<Extension()> _
Public Sub Save(ByVal b As Bitmap, ByVal FileName As String, ByVal Compression As Long, ByVal MimeType As String)
    Dim Params As EncoderParameters = New EncoderParameters(2)
    Dim CodecInfo As ImageCodecInfo = GetEncoderInfo(MimeType)

    Params.Param(0) = New EncoderParameter(Encoder.RenderMethod, EncoderValue.RenderProgressive)
    Params.Param(1) = New EncoderParameter(Encoder.Quality, Compression)

    b.Save(FileName, CodecInfo, Params)
End Sub

这不起作用.它没有被保存为渐进式.我怎么能这样做,也可以指定nr的通行证.

Answer 1

据我所知,它不受支持.我已经尝试过这里和这里建议的代码,并得到了这个C#代码:

using (Image source = Image.FromFile(@"D:\temp\test2.jpg")) {

  ImageCodecInfo codec = ImageCodecInfo.GetImageEncoders().First(c => c.MimeType == "image/jpeg");

  EncoderParameters parameters = new EncoderParameters(3);
  parameters.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L);
  parameters.Param[1] = new EncoderParameter(System.Drawing.Imaging.Encoder.ScanMethod, (int)EncoderValue.ScanMethodInterlaced);
  parameters.Param[2] = new EncoderParameter(System.Drawing.Imaging.Encoder.RenderMethod, (int)EncoderValue.RenderProgressive);

  source.Save(@"D:\temp\saved.jpg", codec, parameters);
}

设置隔行和逐行模式,它仍然保存常规基线JPEG.我尝试了任何设置和其他设置(非隔行扫描和非渐进式)的任意组合,并且在生成的图像文件中根本没有看到任何差异.

我没有发现任何人说他们实际上已经设法在.NET中保存渐进式JPEG的任何回复.

两个ScanMethodInterlaced和RenderProgressive参数值仅被描述为"未在GDI +版本1.0中使用".在 文档中.